1. Field of the Invention
The present invention relates to a planetary gear reducer for a vehicular steering apparatus, and more particularly to a planetary gear reducer for a vehicular steering apparatus, in which backlash compensation members are mounted on a sun gear, a planetary gear, and a ring gear for a planetary gear reducer to be capable of compensating for an inter-gear backlash for a bi-directional input, minimizing rattle noise, and reducing damage of the gears and rattle noise caused by reverse input transferred to an output shaft.
2. Description of the Prior Art
In general, a planetary gear reducer includes a sun gear, a planetary gear supported by a carrier and circumscribing the sun gear, and a ring gear, to which the planetary gear is inscribed.
The planetary gear reducer has advantages in that it can be simply configured, and since each of constituent gears consisting of the sun gear, the planetary gear, and ring gear is set to an input shaft or an output shaft, a speed reduction ratio (or a speed increasing ratio) can be easily changed. Thus, the planetary gear reducer is frequently used for vehicular steering apparatuses.
However, in such a planetary gear reducer, inter-gear backlashes exist between the gear teeth of the sun gear and the gear teeth of the planetary gear, and between the gear teeth of the planetary gear and the gear teeth of the ring gear.
More specifically, a backlash refers to a space produced behind gear teeth meshed with each other when the gear teeth of a first gear are meshed with the gear teeth of a second gear.
Meanwhile, in a gear apparatus in which a driving gear and a driven gear are meshed with each other, no problem will occur when the speeds of the driving gear and the driven gear are constant. However, when the speeds become changed due to a certain reason, rattle noise may be generated due to an inter-gear backlash.
In the case of a vehicular steering apparatus, the rattle noise generated due to the inter-gear backlash causes displeasure at the time of steering, and gradually increases as the wear on the gear teeth progresses.
Accordingly, research has been performed on a backlash compensation structure capable of compensating for the inter-gear backlash so as to reduce the rattle noise.
As a conventional backlash compensation structure, U.S. Pat. No. 6,148,684 (issued on Nov. 21, 2000) (hereinafter, referred to as “prior art”) discloses an “anti-backlash gear.”
As illustrated in FIG. 1, the prior art includes a driving gear 10 and a driven gear 20 having gear teeth, of which the number is equal to the number of the gear teeth of the driving gear 10, in which each of the gears 10 and 20 is formed with a plurality of holes 30.
In addition, a plurality of spring rods 41 are mounted in a circular load ring 40, and the spring rods 41 are inserted through holes 30 that are formed in the driving gear 10 and the driven gear 20.
Accordingly, when the driving gear 10 is driven, the driven gear 20 compensates for the inter-gear backlash through the elastic variation of the spring rods 41.
The prior art may compensate for the inter-gear backlash and thus, reduce the rattle noise. However, since the load ring, the spring rods, and other separate components are used, the prior art has a problem in that the entire structure of the gears has an increased thickness and an increased weight, and the number of components increases, which causes the increase of manufacturing costs.